1. Field of the Invention
The present invention relates to three-dimensional image display systems and, more particularly, to an autostereoscopic multiview three-dimensional image display system.
2. Description of the Related Art
A multiview (or multiperspective) three-dimensional imaging system provides multiple pairs of two-dimensional images of a three-dimensional object. In order to simulate binocular parallax, one of any given pair of two-dimensional images is intended for the right eye of a viewer, while the other image of the given pair, different from the first, is intended for the left eye of the viewer. In order to simulate motion parallax, each of the pairs of images is captured from a different view (or perspective) of the object. A multiview three-dimensional imaging system thus provides only an illusion of a three-dimensional image, not a real three-dimensional image, since the multiview imaging system does not recreate the three-dimensional pattern of light rays emanating from the object, as does a. holographic imaging system.
In contrast to two-dimensional images, multiview three-dimensional images can be viewed only within a viewing zone of finite spatial extent. An important feature of a multiview three-dimensional image display system is accordingly the size and shape of the viewing zone formed. Another important feature is the method employed to display the multiview images. The multiple two-dimensional images of the object may, for example, be time-multiplexed, which involves sequentially displaying the multiple images at the frame rate of the display system.
FIGS. 1(a) and 1(b) provide plan and side views of a conventional multiperspective three-dimensional imaging system that utilizes time-multiplexing. Images 2 captured from various perspectives of a three-dimensional object are displayed on an image display device 1 and projected onto a screen 3 via projection optics 4 and a spatial light modulator 5.
The spatial light modulator, a multi-strip liquid crystal display(LCD) disposed at the exit pupil of the projection optics, comprises multiple parallel strip-like liquid crystal shutters, where the number of shutters is equal to the number of views or perspectives. The strip-like shutters, in effect, divide the exit pupil of the projection optics into multiple strips. The sequential openings and closings of the strip-like shutters are synchronized with the sequential display of the multiperspective images: a given strip-like shutter is open only when the image from the view or perspective corresponding to that shutter is to be displayed and is closed at all other times.
The screen, which may be a holographic screen, distributes the multiview images transmitted by the liquid crystal shutters over a plurality of viewing zones 6a, 6b, . . . , 6n. Each of the viewing zones is, in effect, divided by the strip-like shutters. The multiview images may be generated by a multiview camera 7 or a computer 8 and time-multiplexed by a signal converter 9. The spatial light modulator is itself driven by a shutter driver 10 that is synchronized with the sequence of multiview images by the signal converter.
The multiview three-dimensional imaging system illustrated in FIG. 2 is capable of displaying full-color images (Jung-Young Son, Victor G. Komar, You-Seek Chun, Sergei Sabo, Victor Mayorov, L. Balasny, S. Belyaev, Mihail Semin, M. Krutik, and Hyung-Wook Jeon, "A multiview 3-D imaging system With full color capabilities," SPIE Proc. Stereoscopic Displays and Virtual Reality IV in Electronic Inmaging'98, San Jose, USA. Jan., 1998, pp. 24-30 3295A-31). An image generation component 18 comprises three image display devices 13a-13c and a dichroic beam splitter 15. The image display devices 13a-13c, each of which is disposed at a different surface of the beam splitter, display three primary color images 14a-14c, respectively. The beam splitter combines the three primary color images into a full-color image. The full-color image is projected onto the image projection screen 3 after transiting a fourth surface of the beam splitter, projection optics 16, and a spatial light modulator 17, in that order.
To display N time-multiplexed multiview images without flicker, where each of the multiview images is provided by a different one of N identical individual display devices, a multiview image display system must have the same spatial resolution as each of the multiview images and a frame rate N times that of each of the individual display devices. Thus, to display eight multiview images without flicker, each provided by a conventional entertainment television, the frame rate of the multiview image display system must be greater than 240 frames/s, since the frame rate of the conventional NTSC TV is 30 frames/s.
Display devices suitable for the time multiplexing method, include the cathode ray tube(CRT), the digital micromirror device, and the ferroelectric LCD. Of these, the CRT has the best resolution and is easiest to use. Although CRTs can display as many as 28 multiview images, such a CRT is not commercially available. The marginal frame rate of the commercially available CRT for a flickerless image is 240 frames/s, which can display, 8 view images with the resolution of NTSC TV. To display a greater number of images, the development of a new display device with a faster response speed is needed, which requires more time and cost than those required in the development of a higher resolution flat display device for the space multiplexing method.